And this http://forums.whirlp...s.cfm?t=1582172 shows the fastest random 4k R/W are class 2 and class 4 cards.I have just tested the sandisk class 4 that the phone came with and my Play class 10, I tested 4k random r/wSandisk class 4 = 1.985/0.015Play class 10 = 2.807/0.016So both are pretty awful when it comes to random 4k write - "apparently the 4k write speed is most important"..